As the result of continuous advances in technology, particularly in the area of networking, such as the Internet, there is an increasing demand for communications bandwidth. For example, the transmission of images or video over the Internet, the transfer of large amounts of data in transaction processing, or videoconferencing implemented over a public telephone network typically require the high speed transmission of large amounts of data. As applications such as these become more prevalent, the demand for communications bandwidth will only increase.
Optical fiber is a transmission medium that is well suited to meet this increasing demand. Optical fiber has an inherent bandwidth much greater than metal-based conductors, such as twisted-pair or coaxial cable; and protocols such as Synchronous Optical Networking (SONET) have been developed for the transmission of data over optical fibers.
Optical fiber is used to form optical networks that carry data, voice, and video using multiple wavelengths of light in parallel. Light is routed through the network from its originating location to its final destination. Since optical networks do not generally have a single continuous optical fiber path from every source to every destination, the light is switched as it travels through the optical network. Previously, this switching was accomplished using optical-electrical-optical (“OEO”) systems, where a light signal was converted to an electrical signal, switched electrically, and then output optically. Because in OEO systems the signal must be converted from optical to electrical, switched, then converted back to optical, OEO systems are relatively large, complex, and expensive. More seriously, the OEO systems are slower than purely optical systems, and consequently introduce undesirable bottlenecks.
Much effort is being expended on the development of all-optical cross-connect switching systems, some of which employ arrays of electrostatically, electromagnetically, piezoelectrically, or thermally actuated mirrors. Digitally controlled mirrors with on and off states can be used to switch between small numbers of ports while analog controlled mirrors can be implemented with a small or a large number of ports. Analog controlled mirrors require bi-axial actuation; unfortunately, most electrostatic actuators used to position these mirrors suffer from relatively low torque, and consequentially require relatively high supply voltages to produce sufficient motion. The lack of torque also renders electrostatic actuators very sensitive to vibrations. There is therefore a need for a bi-axial actuator that operates at lower voltages and is relatively insensitive to vibration.